Finding specific serum biomarkers linked to rheumatoid arthritis (RA) can help us understand the
course of the disease, and the prognosis. Here, we aimed to explore the potential use of arginine,
ornithine, tryptophan, citrulline, serotonin and several other biochemical markers for early
diagnosis of rheumatoid arthritis (RA). We examined serum samples from 30 controls and 60 RA
patients to achieve this goal. According to our findings, there was a statistically significant difference
in the serum levels of ornithine and arginine between RA patients and controls, with
higher ornithine and lower arginine in RA patients compared to controls. Furthermore, we found
that only patients with high disease activity index had considerably greater levels of serotonin.
Additionally, we found that using arginine alone can predict RA disease with 96.7% sensitivity
and 80.8 % specificity, while ornithine can predict RA disease with 100% sensitivity and 66.7%
specificity. Interestingly, the ornithine to arginine ratio (OR/AR) could identify people with RA
disease with 100% sensitivity and 83.3% specificity and this clear discrimination is not affected
by the disease index or duration. Hence, RA patients can be distinguished using the ornithine to
arginine ratio as a biomarker, which has higher specificity than each analyte alone. Our results
can undoubtedly serve as a foundation for additional research and multicenter studies in the
future to support accurate therapeutic management strategies for RA patients.